JPH08137125A - Toner for developng electrostatic latent image - Google Patents

Abstract

PURPOSE: To improve variance in the distribution of electric charges on the surface of a toner contg. toner matrix particles and to attain uniform electrostatic charge by specifying the difference between the absolute value of the ξ-potential of the surfaces of the toner matrix particles and that of the surface of the toner. CONSTITUTION: This toner consists essentially of toner matrix particles contg. a bonding resin and a colorant and inorg. fine particles selectively fixed on the surfaces of the toner matrix particles. The difference between the absolute value of the ξ-potential of the surfaces of the toner matrix particles and that of the surface of the toner is >=0.5. The particle diameter of the toner matrix particles is preferably 7-12μm. The inorg. particles are preferably one kind among particles of silica, titanium oxide, zinc oxide, aluminum oxide, zirconium oxide or magnesium oxide and the pref. amt. of the inorg. particles is 0.05-1.5wt.% of the amt. of the toner matrix particles. The bonding resin is, e.g. polystyrene or polyethylene. A mixture of two or more kinds of such resins may be used. The colorant is, e.g. carbon black or a copper phthalocyanine pigment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing an electrostatic latent image, and more particularly to a toner for developing an electrostatic latent image for electrophotography.

[0002]

2. Description of the Related Art Generally, a surface of a toner for developing an electrostatic latent image has a mixture of positively charged sites and negatively charged sites. In order to obtain a toner having a desired charge amount, for example, a toner having a positive charge, as a method of erasing the negative charge sites on the toner surface, inorganic particles having a positive charge are added to the surface of the toner by a Henschel mixer, a turbula mixer, or a super mixer. A method of fixing with a device such as a mixer is known. However,
In these methods, the fixing of the inorganic particles is insufficient, and the inorganic particles are easily detached, and the effect is insufficient.

In order to prevent detachment of inorganic particles, a method of fixing them by a mechanical impact force has been tried. in this way,
Although the problem of detachment of the inorganic fine particles is improved, the problem of fog in the image remains. When the mechanical impact force is too strong, the spheroidization of the mother particles progresses to expose the opposite charging sites, and the inorganic particles are embedded in the toner mother particles, so that the toner having a desired charge amount is obtained. Therefore, there is a problem that the image is fogged or the toner is scattered.

[0004]

The problem to be solved by the present invention is to improve the dispersion of the surface charge of the toner and obtain a uniformly charged toner. Another problem to be solved by the present invention is to prevent fogging and toner scattering.

[0005]

A toner for developing an electrostatic latent image according to the present invention has toner mother particles containing a binder resin and a colorant, and is selectively fixed on the surface of the toner mother particles. A toner including inorganic fine particles. At this time, the difference between the absolute value of the zeta potential on the surface of the toner mother particle and the zeta potential on the toner surface is 0.5 or more.

The particle diameter of the toner base particles is preferably in the range of 7 to 12 μm. The inorganic particles are preferably one selected from silica, titanium oxide, zinc oxide, aluminum oxide, zirconium oxide, and magnesium oxide. The amount of the inorganic particles is preferably in the range of 0.05 to 1.5% by weight based on the toner mother particles.

Hereinafter, the present invention will be described in detail. Examples of the binder resin include polystyrene, polyethylene,
Various thermoplastic resins such as polypropylene, vinyl resins, polyacrylates, polymethacrylates, polyvinylidene chloride, polyacrylonitrile, polyethers, polycarbonates, thermoplastic polyesters, cellulosic resins, and copolymers of these monomers, or modified Thermosetting resins such as acrylic resin, phenolic resin, melamine resin, urea resin and the like can be mentioned. You may use it, mixing 2 or more types of these.

As the colorant, dyes and pigments suitable for various systems are used, and examples thereof include carbon black, copper phthalocyanine thread pigment, azo lake pigment, and benzidine thread pigment. The toner according to the present invention may contain magnetic powder. As the magnetic powder, those usually used may be used, such as iron, manganese, nickel, cobalt and other metal powders, magnetite, copper-zinc ferrite, barium-zinc ferrite, manganese-zinc ferrite, lithium-zinc ferrite. , Various ferrates such as magnesium-manganese ferrite, magnesium-copper-zinc ferrite, barium-nickel-zinc ferrite and barium-copper-zinc ferrite are preferable. Particularly, magnetite is preferably used. The particle size of these magnetic powders is preferably 0.8 μm or less, more preferably 0.1 μm or less.

Further, the toner mother particles may contain a charge control agent or a release agent, if necessary. The amount to be used, the addition method, etc. may be in accordance with a conventional method. As the charge control agent, those generally used may be used. For example, as the charge control agent for positive charge control, an organic compound having a basic nitrogen atom, for example, a basic dye, aminopyrine, or a pyrimidine compound is used. , Polynuclear polyamino compounds, aminosilanes and the like. As the charge control agent for negative charge control, nigrosine base, oil black, oil-soluble dyes such as spirone black, metal-containing azo dyes, metal salts of naphthenic acid, metal salts of alkylsalicylic acid, fatty acid soaps, resin acid soaps, etc. can give.

Examples of the releasing agent include low molecular weight polypropylene and the like. The particle size of the toner mother particles used in the present invention is preferably in the range of 7 to 12 μm. Particle size is 7
If it is smaller than μm, the image density may be insufficient. If the particle size is larger than 12 μm, the resolution of the image may be poor.

The surface of the toner base particles is provided with inorganic fine particles that are selectively fixed. The inorganic particles have a charge opposite to the desired charging site on the surface of the toner base particle, and the mechanical impact force is applied to the charging site (desired charging property and reverse charging site) to be erased on the surface of the toner base particle. It is fixed. In the electrostatic latent image developing toner according to the present invention, the difference between the absolute value of the zeta potential on the surface of the toner mother particles and the zeta potential on the toner surface is 0.5 or more. If the difference in surface zeta potential is less than 0.5, the fixing of the inorganic particles becomes insufficient and a toner having a desired zeta potential cannot be obtained. In addition, the inorganic particles are buried in the toner mother particles,
Because the mother particle becomes spherical and a new interface appears,
The toner may be unevenly charged.

The zeta potential can be measured, for example, by a measuring instrument "DELSA44" manufactured by Coulter Electronics Co.
It is better to use "0". As a means for selectively fixing the inorganic fine particles, the surface modification device such as hybridization, ongmill, mechanomill or the like can be used. The conditions for fixation by the surface modification device differ depending on the device used, but the rotation speed is 1200 rpm to 8 rpm.
000 rpm is preferable, rotation speed is 2000 r
More preferably, it is pm to 3600 rpm. If the rotation speed is slower than 1200 rpm, the fixing of the inorganic particles becomes insufficient, a toner having a desired zeta potential cannot be obtained, or the inorganic fine particles are fixed as they are aggregated.
Further, when the rotation speed is higher than 8000 rpm, the inorganic particles are embedded in the toner mother particles, or the mother particles are spherical and a new interface appears, so that the toner is not uniformly charged.

The time for the fixing treatment by the surface modification device is preferably 30 seconds to 180 seconds, 60
More preferably, it is from seconds to 90 seconds. When the processing time is longer than 180 seconds, the inorganic particles are embedded in the toner mother particles, or the mother particles are spheroidized and new interfaces appear, resulting in non-uniform charging of the toner. Also,
When the time is shorter than 30 seconds, the fixing of the inorganic particles becomes insufficient, and a toner having a desired zeta potential cannot be obtained.

Examples of the above-mentioned inorganic particles include silica, titanium oxide, aluminum oxide and the like. In particular, hydrophobic silica is preferable in that it is excellent in environmental resistance and greatly contributes to improvement of toner fluidity and charging stability. , Preferably used. Specific examples of the inorganic fine particles include hydrophobic silica such as “RA130H”, “R974”, and “R9”.
72 "," R202 "," R805 "," R812 "
(These are products of Nippon Aerosil Co., Ltd.), "Taranox 50
0 "(manufactured by Tarco)," Cab-O-Sil "," M- "
5 "," MS-7 "," MS-75 "," HS-5 ",
Examples include "EH-5", "S-17", "TS-720" (all manufactured by Cabot) and "HVA-2150" (manufactured by Hoechst & Wacker). For titanium oxide, "Titanium Dioxide P25", "T-805" (above, manufactured by Nippon Aerosil Co., Ltd.), "Titanium Black 12S"
(Manufactured by Mitsubishi Metals), etc. With aluminum oxide,
"Aluminium Oxide C" (Made by Nippon Aerosil Co., Ltd.)
Etc. In addition to these, zinc oxide, zirconium oxide,
Magnesium oxide or the like can also be used.

The amount of the inorganic particles used is preferably in the range of 0.05 to 1.5% by weight, and more preferably in the range of 0.1 to 1.2% by weight, based on the toner mother particles. It is more preferable that there is. If the amount is less than 0.05% by weight, a toner having a desired zeta potential may not be obtained or the charging polarity may become non-uniform. Also, 1.
If it is more than 5% by weight, insufficient image density may occur due to overcharge.

The particle size of the inorganic fine particles is 0.002 to
It is preferably in the range of 0.200 μm, and 0.00
The range of 5 to 0.100 μm is more preferable. If the particle size is smaller than 0.002 μm, the image density may be poor and drum filming may occur. If the particle size is larger than 0.200 μm, it may be difficult to control the chargeability of the toner.

[0017]

FIG. 1 shows the case where only the toner mother particles are treated by the same surface reforming apparatus A and the case where the inorganic mother fine particles are introduced at the same time as the toner mother particles and subjected to the fixing treatment B. 5 is a graph showing the relationship between time and zeta potential. In the case of A, the spheroidization of the mother particles proceeds as the treatment time becomes longer, and the oppositely charged sites of the mother particles are exposed, so that the zeta potential increases. In the case of B, the zeta potential decreases as the inorganic fine particles are fixed and the reverse charging site on the surface of the mother particle disappears. This zeta potential shows a minimum value at a certain point, and thereafter, as the degree of immobilization becomes stronger, the inorganic fine particles are buried in the surface of the mother particle, so that the zeta potential increases and approaches the state of A.

In the present invention, by measuring the difference in zeta potential, the degree of immobilization of the inorganic fine particles adhered to the surface of the toner base particles (the amount, the degree of embedding in the toner base particles, etc.) is controlled. That is, when the difference V _S between the absolute value of the zeta potential in the case of A and the absolute value of the zeta potential in the case of B is 0.5 or more in the same processing time,
The number of reverse charging sites with respect to the desired charge amount on the toner surface is reduced, and the variation in the surface potential of the toner can be improved. As a result, a toner having a uniform charge amount can be obtained.

[0019]

[Examples] Example 1 [Production of toner mother particles] (Toner composition) Parts by weight Binder resin Styrene acrylic resin 100 Magnetic powder (colorant) Magnetite (BL-220, manufactured by Titanium Industry Co., Ltd.) 60 Charge control agent FCA -201-PZ (manufactured by Fujikura Kasei Co.) 3 Release agent Piscol 550 (manufactured by Sanyo Kasei Co.) 3 The above composition was mixed, melt-kneaded, pulverized and classified to produce toner mother particles having an average particle diameter of 11 μm. did.

To the toner base particles, fine particles of hydrophobic silica (HVK-2150, manufactured by Hoechst & Wacker Co., Ltd.) of 1.0% by weight based on the toner base particles were added, and the particles were placed in a hybridizer machine and 2400 rpm. 6 rpm
Toner 1 was obtained by mixing for 0 seconds. Example 2 Toner 2 was obtained in the same manner as in Example 1 except that the rotation speed was set to 2800 rpm.

Example 3 Toner 3 was obtained in the same manner as in Example 1 except that the mixture was carried out for 120 seconds. Example 4 Toner 4 was obtained in the same manner as in Example 1 except that mixing was performed for 150 seconds. Example 5 Toner 5 was obtained in the same manner as in Example 1 except that mixing was performed for 30 seconds.

Comparative Example 1 Comparative Toner 1 was obtained in the same manner as in Example 1 except that mixing was carried out for 10 seconds. Comparative Example 2 Comparative Toner 2 was obtained in the same manner as in Example 1 except that mixing was performed for 240 seconds. The toners 1 to 5 and the comparative toners 1 and 2 thus obtained were used for forced deterioration evaluation. The results are shown in Table 1.
It was shown to.

[Method of Measuring Zeta Potential] Measuring device "DE
LSA440 ”(manufactured by Coulter Electronx) was used for measurement. [Forced deterioration evaluation method] In the forced deterioration evaluation method, 50 g of a toner sample was put in a non-contact type magnetic one-component developing unit and set in an image evaluation standard machine to obtain an initial image sample.
The unit was taken out and set in an aging device. The rotation speed of the developing sleeve is 50 rpm,
Aging was performed for 2 hours. After aging, the toner was sampled from the same unit to measure the coverage area ratio.

[Measurement Method of Covering Area Ratio] An enlarged photograph of the toner was taken with an electron microscope, and the area ratio of the inorganic particles on the toner surface was calculated from the photograph using an image analyzer.

[0025]

[Table 1]

When the difference in zeta potential is 0.5 or more, it can be seen that the coated area ratio after the forced deterioration test is not significantly reduced and the inorganic fine particles are firmly fixed. Further, when the difference in zeta potential is smaller than 0.5, the coverage ratio after the forced deterioration test is considerably reduced, and it is understood that the degree of adhesion of the inorganic fine particles is weak.

[0027]

The electrostatic latent image developing toner of the present invention has an absolute value of the zeta potential on the surface of the toner base particles and a toner surface zeta potential when the inorganic fine particles are selectively fixed to the surface of the toner base particles. By controlling so that the difference between and is 0.5 or more, it is possible to improve the variation in toner surface charge. As a result, a uniformly charged toner can be obtained.

When the amount of the inorganic particles used is within the range of 0.05 to 1.5% by weight based on the toner mother particles, a more uniformly charged toner can be obtained. Since the electrostatic latent image developing toner of the present invention is uniformly charged, it is possible to prevent fog on the image and toner scattering.

[Brief description of drawings]

FIG. 1 is a graph illustrating the relationship between processing time and zeta potential.

[Explanation of symbols]

The difference between the zeta potentials of the zeta potential of A and B in the case V _S same processing time which has been subjected to fixing treatment A toner mother When particles only were treated B toner base particles and the inorganic fine particles and introduced simultaneously

Claims (4)

[Claims] 1. A toner comprising toner mother particles containing a binder resin and a colorant, and inorganic fine particles selectively fixed to the surface of the toner mother particles, wherein A toner for developing an electrostatic latent image, wherein the difference between the absolute value of the zeta potential and the absolute value of the toner surface zeta potential is 0.5 or more. 2. The toner for developing an electrostatic latent image according to claim 1, wherein the particle diameter of the toner mother particles is in the range of 7 to 12 μm. 3. The electrostatic latent image development according to claim 1, wherein the inorganic particles are one selected from silica, titanium oxide, zinc oxide, aluminum oxide, zirconium oxide and magnesium oxide. For toner. 4. The electrostatic latent image according to claim 1, wherein the amount of the inorganic particles is in the range of 0.005 to 1.5% by weight based on the toner mother particles. Toner for development.